ABSTRACT: Liver fibrosis and its advanced form, cirrhosis, can occur in virtually all types of chronic liver disease (CLD) and are major health problems due to their high mortality rates and predisposition to cause liver failure, portal hypertension, and hepatocellular carcinoma (HCC). According to the American Liver Foundation, 5.5 million Americans are currently afflicted with CLD or cirrhosis, and the National Institutes of Health (NIH) reports cirrhosis as the 12th leading cause of death due to disease in America. The long-term goal of this proposal is to understand mechanisms underlying hepatic reparative processes and to discover novel therapy targets for boosting repair and reducing fibrosis. Connective tissue growth factor (CTGF) is a secreted matricellular protein in the Cyr61/CTGF/Nov (CCN) protein family that acts as an extracellular modifier through binding to growth factors, receptors, and the extracellular matrix (ECM). It is transcriptionally activated by transforming growth factor (TGF)-? and the transcriptional co-activator Yes-associated protein (YAP). Overexpression of CTGF has been identified as a hallmark of fibrotic disorders. Our studies have demonstrated the importance of CTGF in hepatic progenitor cell (HPC) response and fibrosis in animal models. In addition, we have found that another negative regulator, miR-133b, targets the 3' UTR of Ctgf mRNA and exhibits anti-fibrotic potential. The hypothesis underlying this proposal is that CTGF promotes HPC mediated fibrotic response through binding to key regulators, whereas CTGF downregulation negatively affects this process. This hypothesis will be tested utilizing our recently developed rat models in the following two specific Aims. AIM I: Determining if deletion of the Ctgf gene by CRISPR/Cas9 mitigates the fibrotic response in alcohol induced rat liver injury models: Transgenic animals deficient for CTGF production will be subjected to chemically induced liver damage. The necessity of CTGF for initiation and progression of liver fibrosis will be evaluated. AIM II: Determining whether miR-133b inhibits HSC activation and subsequent liver fibrosis. The expression pattern of miR-133b during HSC activation and liver fibrosis will be examined. Systemic delivery of miR-133b using an AAV delivery system will be applied in vivo to alcohol damaged rat livers to assess the anti-fibrotic potential of miR-133b. This study will provide new mechanistic insights into the modulation of fibrosis, aimed at the discovery of novel therapeutic strategies and new molecular targets to enhance repair mechanisms and reduce liver fibrosis.